Sex Differences in Stress Response: Classical Mechanisms and Beyond

Connecting the dots: sex, depression, and musculoskeletal health

Depression and multiple musculoskeletal disorders are overrepresented in women compared with men. Given that depression is a modifiable risk factor and improvement of depressive symptoms increases positive outcomes following orthopedic intervention, efforts to improve clinical recognition of depressive symptoms and increased action toward ameliorating depressive symptoms among orthopedic patients are positioned to reduce complications and positively affect patient-reported outcomes. Although psychosocial factors play a role in the manifestation and remittance of depression, it is also well appreciated that primary biochemical changes are capable of causing and perpetuating depression. Unique insight for novel treatments of depression may be facilitated by query of the bidirectional relationship between musculoskeletal health and depression. This Review aims to synthesize the diverse literature on sex, depression, and orthopedics and emphasize the potential for common underlying biological substrates. Given the overrepresentation of depression and musculoskeletal disorders among women, increased emphasis on the biological drivers of the co-occurrence of these disorders is positioned to improve women's health.

Prefrontal cortex-nucleus reuniens-hippocampus network exhibits sex-differentiated responses to stress and antidepressant treatment in rats

RATIONALE

Depression is a serious psychiatric disease, which is diagnosed twice as frequently in women than men. We have recently shown that lesioning or inactivation of the nucleus reuniens (RE), which interconnects the prefrontal cortex (PFC) and hippocampus, promoted resilience to stress in males, exerts an antidepressant effect in the Forced Swim Test (FST) and prevents the development of behavioral and neurobiological alterations induced by the chronic mild stress model of depression.

OBJECTIVES

In this study, we expand our findings on the FST in female rats and we investigate whether RE lesion presents sex differences following treatment with two distinct antidepressants, a selective serotonin reuptake inhibitor, i.e. sertraline and a tricyclic antidepressant, i.e. clomipramine.

METHODS

Male and female rats received either a surgical lesion of the RE or sham operation, then treated with vehicle, sertraline (10mg/kg) or clomipramine (10mg/kg) and were subjected to the FST. Activation of key brain areas of interest (PFC, Hippocampus and RE) were measured by c-Fos immunoreactivity.

RESULTS

RE lesion induced an antidepressant-like phenotype in both female and male rats, confirming its crucial role in the stress response. Similarly to RE lesion, sertraline treatment resulted in increased swimming and decreased immobility duration, as well as enhanced head shake frequency, in both sexes. Notably, climbing behavior was increased only following clomipramine treatment. RE area was less active in females compared to male rats and in clomipramine-treated males compared to their corresponding vehicle-group. Activation of the PFC and the CA1 hippocampal area was reduced in clomipramine-treated females, in comparison to vehicle-treated female rats. This effect was not evident in males, which exhibited less activation in the PFC and the hippocampus than females.

CONCLUSION

Re lesion proves equally effective in female and male rats, but sex is highlighted as a pivotal factor in behavioral and treatment response in FST, as well as in related circuit connectivity and activation.

Activation of CRF/CRFR1 Signaling in the Central Nucleus of the Amygdala Contributes to Chronic Stress-Induced Exacerbation of Neuropathic Pain by Enhancing GluN2B-NMDA Receptor-Mediated Synaptic Plasticity in Adult Male Rats

Exacerbation of pain by chronic stress and comorbidity of pain with stress-related disorders such as depression and post-traumatic stress disorder, represent significant clinical challenges. Previously we have documented that chronic forced swim (FS) stress exacerbates neuropathic pain in spared nerve injury (SNI) rats, associated with an up-regulation of GluN2B-containing N-methyl-D-aspartate receptors (GluN2B-NMDARs) in the central nucleus of the amygdala (CeA). However, the molecular mechanisms underlying chronic FS stress (CFSS)-mediated exacerbation of pain sensitivity in SNI rats still remain unclear. In this study, we demonstrated that exposure of CFSS to rats activated the corticotropin-releasing factor (CRF)/CRF receptor type 1 (CRFR1) signaling in the CeA, which was shown to be necessary for CFSS-induced depressive-like symptoms in stressed rats, and as well, for CFSS-induced exacerbation of pain hypersensitivity in SNI rats exposed to chronic FS stress. Furthermore, we discovered that activation of CRF/CRFR1 signaling in the CeA upregulated the phosphorylation of GluN2B-NMDARs at tyrosine 1472 (pGluN2BY1472) in the synaptosomal fraction of CeA, which is highly correlated to the enhancement of synaptic GluN2B-NMDARs expression that has been observed in the CeA in CFSS-treated SNI rats. In addition, we revealed that activation of CRF/CRFR1 signaling in the CeA facilitated the CFSS-induced reinforcement of long-term potentiation as well as the enhancement of NMDAR-mediated excitatory postsynaptic currents in the basolateral amygdala (BLA)-CeA pathway in SNI rats. These findings suggest that activation of CRF/CRFR1 signaling in the CeA contributes to chronic stress-induced exacerbation of neuropathic pain by enhancing GluN2B-NMDAR-mediated synaptic plasticity in rats subjected to nerve injury. PERSPECTIVE: Our present study provides a novel mechanism for elucidating stress-induced hyperalgesia and highlights that the CRF/CRFR1 signaling and the GluN2B-NMDAR-mediated synaptic plasticity in the CeA may be important as potential therapeutic targets for chronic stress-induced pain exacerbation in human neuropathic pain. DATA AVAILABILITY: The data that support the findings of this study are available from the corresponding author upon reasonable request.

Pre-exercise cryotherapy reduces myoglobin and creatine kinase levels after eccentric muscle stress in young women

Introduction: The aim of this study was to investigate the effect of pre-exercise whole-body cryotherapy (WBC) on muscle damage indicators following eccentric treadmill exercise in young women. Methods: Twenty-seven participants underwent two 1-h downhill treadmill runs, replicating 60% of their maximal oxygen uptake, with a 4-week intermission for recovery and treatment application. In this intermission, one group underwent 20 sessions of WBC, delivered five times a week at -120°C for 3 min each, while the comparison group received no such treatment. Markers of muscle injury-serum myoglobin concentration, creatine kinase and lactate dehydrogenase activity and also uric acid, and cell-free DNA concentration-were measured before and after downhill runs. Results: The study observed a notable reduction in post-exercise myoglobin and CK levels in the WBC group after the second running session. Discussion: The results suggest that WBC can have a protective effects against muscle damage resulting from eccentric exercise.

Alzheimer's therapeutic development: shifting neurodegeneration to neuroregeneration

Alzheimer's disease (AD), similar to AD-related dementias, is characterized by impaired/lost neuronal structures and functions due to a long progression of neurodegeneration. Derailed endogenous signal pathways and disease processes have critical roles in neurodegeneration and are pharmacological targets in inducing neuroregeneration. Pharmacologically switching/shifting the brain status from neurodegeneration to neuroregeneration is emerging as a new therapeutic concept, one that is not only achievable, but also essential for effective therapy for AD. The results of the pharmacological-induced shift from neurodegeneration to neuroregeneration are twofold: arresting cognitive deterioration (and directing the brain toward cognitive recovery) in established AD, and preventing neurodegeneration through building up cognitive resilience in patients with preclinical or probable AD. In this review, we discuss these new developments in AD pharmacology and relevant clinical trials.